In a long-range land-to-sea (LRLS) communication that uses Variable-Time-Slot-TDMA (VTS-TDMA) and Automatic Repeat Request (ARQ) error-control mechanism in the 5 GHz unlicensed spectrum and includes a Base Transceiver Station (BTS) on land and a Customer Premises Equipment (CPE) out in the sea (for example, on ships) link adaptation procedure is utilized. This procedure enables communication end-points to choose the best Modulation and Coding Scheme (MCS) for a given Radio Frequency (RF) channel condition in order to maximize the throughput. However, using an MCS from a non-optimal link adaptation either over-estimates the throughput leading to an unsuccessful transmission of the data frame or under-estimates the throughput causing an underutilization of the broadband LRLS network. As a result, the rate versus range performance suffers from a non-optimal link adaptation.
Service quality (SLA) maintenance issue for CPEs in LRLS exists when the throughput drops below 3 MBPS, which may happen at smaller distances (reduced cell edge) due to a non-optimal link adaptation. In such a scenario, there is a need to switch data-path to Very Small Aperture Terminal (VSAT) network to maintain SLA. However, network entry/re-entry events may trigger data-path switch back to LRLS network (from VSAT). This switching back and forth of data-paths, between LRLS and VSAT channels may get into unnecessary “flapping” (or ping-pong) effect. Such switching back and forth affects the overall Quality of Experience (QoE). Since the LRLS operates in a shared spectrum, the channel quality becomes unpredictable based on the usage of the shared spectrum by other entities. Further, non-optimal link adaptation may further aggravate the flapping issue post switching of channel from VSAT to LRLS under unfavorable conditions of the LRLS channel.
One of the conventional methods discloses link adaptation procedure with MCS selection and switching using Signal-to-Interference Ratio (SIR) metric. However, in this conventional method, infinite retransmission ARQ in link adaptation model with SIR thresholds is assumed, which are hard to compute in the LRLS system. Another conventional method discloses link adaptation procedure with MCS selection and switching using Block Level Error Ratio (BLER) thresholds. However, in this conventional method, BLER thresholds in link adaptation do not capture ARQ retransmissions of data frames.